Artificial turf and method for producing a turf of this type

ABSTRACT

The present invention relates to an artificial turf ( 1 ) and a method for producing an artificial turf ( 1 ) comprising a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass ( 2 ) protruding from the ground fabric in the shape of pile burls which succeed one another in the warp direction and which each comprise two pile legs ( 2   a ), in which at least three and at most nine weft yarns ( 3 ) are inserted between two successive pile legs ( 2   a ). In particular, each pile leg ( 2   a ) is tied up around a different weft yarn ( 3 ) which are both situated between the two pile legs. As the distance between the two pile legs of a pile burl is only half that of the distance between the pile legs during tufting, the material consumption in terms of plastic grass blade yarn will be greatly reduced. In addition, artificial turf ( 1 ) of this type has the advantage that the pile burls and in particular the plastic blades of grass are evenly distributed across the fabric.

The present invention firstly relates to an artificial turf comprising a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass protruding from the ground fabric in the shape of pile burls which succeed one another in the warp direction and which each comprise two pile legs. Secondly, the present invention relates to a method for producing artificial turf of this type.

Artificial turf is being used increasingly often as a replacement for natural turf because:

-   -   the climatic conditions are not always suitable for natural         turf;     -   the load to which the natural turf is subjected (during sports         events) damages the playing field, which makes it necessary to         leave considerable intervals before using the playing field         again;     -   natural turf requires a lot of care and attention.

It is well known to produce artificial turf in which plastic fibers (blades of grass) are connected to a carrier material in which the plastic blades of grass preferably protrude from the carrier material at right angles. The plastic blades of grass are generally hard and smooth plastic fibers, such as polyolefins (polyethylene, polypropylene and mixtures) or polyamides.

Usually, the carrier material is a textile cloth through which the plastic blades of grass are tufted. This means that a plastic blade of grass is pushed through the cloth by means of a needle to form a loop. On the other side of the textile cloth, a hook takes over the loop which has been produced and takes this loop to the desired level.

The loop is then usually cut through, resulting in the formation of two upright blades of grass.

When producing artificial turf in accordance with the above-described manner, the yarns, and particularly those which form the blades of grass, constitute the main costs of the product. Solutions which result in artificial turf with the same performance while using less yarn will considerably reduce the cost price and are therefore interesting from an economic point of view.

International patent application WO 2004057111 describes the refinement of distributing the plastic blades of grass uniformly across the carrier material by selecting the distance between the rows of piles and the distance between the piles in the same row to be approximately equal and, in addition, to select this distance to be at least 10 mm. This means that only a limited number of yarns have to be used to achieve an optimum distribution. Artificial turf of this type has the drawback that, in order to keep the distance between the rows of blades of grass at at least 10 mm, the plastic blades of grass themselves have to be made from relatively thick filaments or from a considerable number of filaments (e.g. 8×1500 dtex or 8×2000 dtex), which are thus inserted into the artificial turf in the same position. This even distribution of large numbers of filaments ultimately results in a distribution of the plastic blades of grass in the artificial turf which is not really uniform on a monofilament level. The limit on the number of blades of grass in the artificial turf by means of the abovementioned large intermediate distance, in combination with the relatively large blades (e.g. determined by the number of filaments), results in a considerable consumption of grass blade material in order to achieve certain playing properties, such as for example a maximum roll of the ball. This means that a ball on a field which is rolled onto the turf from a height of 1 meter at an angle of 45° has to come to a standstill within a certain distance, e.g. 8 meters or 10 meters, in order to approach the characteristics of natural turf.

Furthermore, it should be noted that the process of tufting the plastic blades of grass currently has the limitation that not less than 120 tufts per meter can be produced in the tuft cloth direction so that there are sufficient loops on the hook and so that, when the subsequent tufts are produced, the pile of the previous loops is not pulled back resulting in very irregular pile or no pile at all. This makes it impossible to produce artificial turf with tuft densities below 10 000 tufts/m² having an even spacing between the various tuft rows.

It is an object of the invention to provide an artificial turf which uses fewer plastic blades of grass and has properties, such as for example regarding roll of the ball, which are similar to the known artificial turf.

The object of the invention is achieved by providing an artificial turf consisting of a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass protruding from the ground fabric in the shape of pile burls which succeed one another in the warp direction and which each comprise two pile legs, in which at least three and at most nine weft yarns are inserted between two successive pile legs. In particular, the two pile legs of a pile burl are tied up around a different weft yarn which are both situated between these two pile legs.

The main difference to the prior art is the fact that, during tufting, the pile legs of a tuft burl (the two legs of a cut tuft loop) lean against one another and are thus situated at virtually the same spot in the cloth. On the back of the tuft cloth, the pile leg of a tuft loop is connected to a pile leg of a subsequent tuft burl, the second pile leg of which also leans against said leg. In this manner, pile warp yarn runs along the back of the fabric in the tuft direction over virtually the entire length of the tufted cloth. With the artificial turf according to the invention, the distance on the back over which pile yarn extends is virtually half the total length. This leads to a significant saving in raw material for the pile warp yarns because there is both less material on the back and also because fewer blades of grass are required to achieve the same performance of the artificial turf due to the improved distribution of the plastic blades of grass.

With a preferred artificial turf according to the invention, the plastic blades of grass protruding from the ground fabric are tied up into the ground fabric by means of a W weave. In this case, the part of the plastic blade of grass which runs on the back of the fabric does not run from one pile leg to the other pile leg on the back of the fabric, but is tied up over one or more weft yarns on the side of the artificial turf pile. This has the advantage that the plastic blades of grass are fastened well in the ground fabric.

With a more preferred artificial turf, for each pile burl, the plastic blade of grass is tied up over at least two weft yarns which are situated between the pile legs of this pile burl on the side of the artificial turf of the fabric. This is in particular achieved by means of a 5/12 W weave in which there are 5 weft yarns between the two pile legs of a pile burl.

According to another preferred embodiment of the artificial turf according to the invention, for each pile burl, the plastic blade of grass is tied up over three weft yarns which are situated between the pile legs of this pile burl on the side of the artificial turf of the fabric. This is in particular achieved by means of a 7/16 W weave in which there are 7 weft yarns between the two pile legs of a pile burl.

In a particular embodiment of the artificial turf, the pile legs of adjacent rows of piles are offset with respect to one another. This is preferably achieved by means of a satin weave, thus resulting in a further improvement of the distribution of the pile burls. Examples thereof are: 5/12 W weave in satin 6; 7/16 W weave in satin 4; 7/16 W weave in satin 8. This method makes it possible to produce the artificial turf in a more efficient manner for an even distribution than without this offset.

In the case of an artificial turf with 6400 blades of grass/m² and with equidistant rows in both directions, 80 rows of piles/m will be distributed in the weft direction (determined by the weaving reed) and 40 pile burls/m (being 80 pile legs/m) will be used in the warp direction with the method without offset.

By using an offset, it is possible to produce the same 6400 blades of grass/m² using 160 rows of piles/m in the weft direction and only 20 pile burls/m, being 40 pile legs/m, if the pile legs of the adjacent row are offset by half the distance between two pile legs. As a result of the offset, there are only 80 pile legs per row in the warp direction. In the next row, over half a distance between two pile legs, are again 80 pile legs per row. Only half as many weft yarns are required in order to achieve these 20 pile tufts/m and consequently the fabric is produced twice as fast. By applying the same method using 113 rows of piles/m and 28.25 pile burls/m, resulting in 56.5 pile legs/m, an even better uniform distribution is achieved in the two directions with in each case 56.5 artificial turf blades/m. Compared to the method using 80 rows of piles/m without offset, this method still uses a significantly smaller number of weft yarns per running meter and the artificial turf can still be produced more quickly for an even distribution.

In a most preferred embodiment of the artificial turf according to the invention, said turf is woven according to a face-to-face weaving method.

It is another object of the present patent application to provide a method for producing an artificial turf comprising a ground fabric and a number of plastic blades of grass protruding from the ground fabric, in which a bottom and a top fabric are woven according to a face-to-face weaving method, in which the fabrics are made from synthetic weft yarns, synthetic ground warp yarns and grass blade-forming pile warp yarns by means of which pile burls with in each case two pile legs are formed alternately in both fabrics, in which, in each fabric, each pile leg in a row in the warp direction is separated by at least three and at most nine weft yarns from the next pile leg of a plastic blade of grass in this row.

After a pile burl has been formed in the one fabric, a pile burl is formed in the other fabric using the face-to-face weaving technique before the plastic grass blade yarn again forms pile in the one fabric. If the two pile legs of the pile burl in the other fabric are also separated by at least three weft yarns from one another, there are also at least three weft yarns between the pile legs of successive pile burls in the same fabric. (With 5/12 W weave, there are seven weft yarns inbetween; with 7/16 W weave, there are nine weft yarns inbetween).

Compared to the known techniques for producing artificial turf, the method according to the invention offers the following advantages:

-   -   When using, both during weaving and during tufting, plastic         blades of grass of the same thickness and the same pile burl         density, the plastic blades of grass (the consumption of which         is nearly identical in both situations) in the artificial turf         according to the invention are distributed over twice as many         evenly distributed physical points, as a result of which the         performance of the artificial turf improves for the same amount         of material (this means that in order to achieve the same         performance of the artificial turf, the pile burl density can be         reduced which results in a lower consumption of plastic grass         blade material);     -   When using, both during weaving and during tufting, plastic         blades of grass of the same thickness and the same pile burl         density, the method according to the invention uses less         material as the distance between the two pile legs of a pile         burl is only half that of the distance between the pile legs         during tufting, as a result of which the material consumption on         the back is reduced;     -   When using relatively thick yarns with a relatively low pile         burl density and if weaving is carried out at a consumption of         pile material which corresponds to the consumption of pile         material of tufted artificial turf, said relatively thick         integrally formed yarns will result in a better stiffness, a         better resilience and a better roll of the ball than is the case         when the pile legs of the tufts are placed next to one another.         The improved properties and equal consumption again result in         less raw material being required in order to achieve the same         performance of the artificial turf;     -   The plastic blades of grass used are usually composed of several         filaments which are bundled. The relatively thick plastic grass         yarn may be composed of relatively thick filaments of which         fewer are ultimately required. This further increases the         resilience and playing properties, as a result of which the         material consumption can be reduced further while retaining the         same playing properties.

According to a preferred method according to the invention, the purpose of the method is to produce an artificial turf as described above.

In the detailed description given below, the abovementioned characteristics and advantages of an artificial turf and the method for producing it according to the invention are explained in more detail. The purpose of this description is only to explain the general principles of the present invention in more detail and therefore nothing in this description should be interpreted as limiting the area of application of the invention or of the patent rights claimed in the claims.

Reference numerals are used in this description to refer to the attached FIGS. 1 to 3, in which:

FIG. 1 shows a diagrammatic representation of an artificial turf with tufted blades of artificial grass according to the prior art;

FIG. 2 shows a cross section through the artificial turf represented in FIG. 1;

FIG. 3 shows a diagrammatic representation of an artificial turf according to the invention.

Due to their high durability, artificial turfs are being used increasingly often in sports these days. In addition, heavily used artificial turfs do not suffer from a loss of quality due to weather conditions or due to being played on, so that such fields can be played on virtually without restriction.

The prior-art artificial turf pitches are composed of tufted artificial turf. This known artificial turf, as illustrated in FIGS. 1 and 2, comprises a base fabric and a number of plastic blades of grass (5) protruding from this base fabric. The plastic blades of grass (5) are connected to the base fabric (for example a textile cloth) by means of reciprocating tuft needles and hooks, onto which the tuft burls are transferred from the needles. However, this known technique has the drawback that in each case two tuft legs (5) of a plastic blade of grass are positioned right next to one another, which indeed do not act a single blade of grass of double thickness due to the limited distance between them. This can be seen in FIG. 2.

The artificial turf (1) according to the present invention and as illustrated in FIG. 3 consists of a ground fabric and a number of plastic blades of grass (2) protruding out of the ground fabric in the shape of pile burls which succeed one another in the warp direction and which each comprise two pile legs. The ground fabric consists of synthetic, moisture-resistant ground warp yarns and weft yarns (3). In addition to the plastic blades of grass and the weft yarns, it is also possible to provide tension warp yarns (4) in the ground fabric, which ensure that the weft yarns are layered, as well as binding warp yarns (not illustrated in the figure) which regularly intersect with each other, the weft yarns being situated between the intersecting binding warp yarns.

The invention is characterized by the fact that at least three and at most nine weft yarns (3) are inserted between two successive pile legs (2 a). In the case of the artificial turf illustrated in FIG. 3, five weft yarns (3) are inserted between two successive pile legs. This is preferably achieved by means of the technique of the W weave in face-to-face weaving: this means that the plastic blades of grass consist of pile burls which each consist of two pile legs, with at least three weft yarns (3) and at most nine weft yarns being present between the pile legs and there also being at least five weft yarns and at most eleven weft yarns between the pile legs of successive pile burls. Each pile leg (2 a) is tied up around a different weft yarn (3 a) which are both situated between the two pile legs. Furthermore, the plastic grass blade section (2 b) which connects the two pile legs to one another is tied up in the ground fabric over at least one additional weft yarn (3 b) between the two pile legs.

When artificial turf is woven in accordance with the method according to the invention and according to the face-to-face weaving technique in a W weave, the two pile legs (2 a) of a tuft are separated from one another over a number weft yarns and therefore over a certain distance. The pile yarn (the plastic blade of grass) then moves to the other fabric in order to also insert two pile legs (2 a) in a W weave as a plastic blade of grass (2) and to return to the first fabric in order to insert two pile legs (2 a) at a distance from one another as a plastic blade of grass (2), again in W weave.

Where the two pile legs together form one tuft (one blade of grass) in one location during tufting, according to the method of the present invention, the same amount of pile is produced in two locations which are a distance apart. With the same material consumption as in the prior art and with the same distance between the rows in the warp direction for weaving as between the needles during tufting, in accordance with the method according to the invention there will be blades of grass in twice as many locations in the warp direction compared to the tufted turf where the blades of grass are situated in the direction in which the tuft cloth moves.

When turf is woven according to the current ½V technique, the two pile legs are also next to one another separated by one weft yarn, as a result of which the two pile legs are virtually next to one another and appear as a single blade of grass. Compared to this prior art, the method of the invention offers the same advantages as the prior art with respect to tufting, especially if the ½V technique is used for intermediate distances between the pile legs of more than 10 mm.

Furthermore, only that part of the plastic blade of grass which runs between two upright plastic blades of grass of the same pile burl runs on the back of the fabric, while there is no material on the back between two upright plastic blades of grass from a different pile burl, thus resulting in a further reduction in the consumption of material. 

1. An artificial turf (1) comprising a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass (2) protruding from the ground fabric in the shape of pile burls which succeed one another in the warp direction (K) and which each comprise two pile legs (2 a), wherein at least three and at most nine weft yarns (3) are inserted between two successive pile legs (2 a).
 2. The artificial turf (1) as claimed in claim 1, characterized in that the plastic blades of grass (2) protruding from the ground fabric are tied up into the ground fabric by means of a W weave.
 3. The artificial turf (1) as claimed in claim 1, characterized in that, for each pile burl, the plastic blade of grass (2) is tied up over at least two weft yarns (3) which are situated between the pile legs (2 a) of this pile burl on the side of the artificial turf of the fabric.
 4. The artificial turf (1) as claimed in claim 1, characterized in that, for each pile burl, the plastic blade of grass (2) is tied up over three weft yarns (3) which are situated between the pile legs (2 a) of this pile burl on the side of the artificial turf of the fabric.
 5. The artificial turf (1) as claimed in claim 1, characterized in that the pile legs (2 a) of adjacent rows of piles are offset with respect to one another.
 6. The artificial turf (1) as claimed in claim 1, characterized in that said turf (1) is woven according to a face-to-face weaving method.
 7. A method for producing an artificial turf (1) comprising a ground fabric and a number of plastic blades of grass (2) protruding from the ground fabric, characterized in that a bottom and a top fabric are woven according to a face-to-face weaving method, in which the fabrics are made from synthetic weft yarns (3), synthetic ground warp yarns and grass blade-forming pile warp yarns (2) by means of which pile burls with in each case two pile legs (2 a) are formed alternately in both fabrics, in which, in each fabric, each pile leg in a row in the warp direction (K) is separated by at least three and at most nine weft yarns (3) from the next pile leg of a plastic blade of grass (2) in this row.
 8. The method as claimed in claim 7, characterized in that the purpose of said method is to produce an artificial turf (1) as claimed in claim
 1. 